Modern skyscrapers often have continuous horizontal window areas extending around the building exterior. These areas are filled by glass panels which are arranged side-by-side with only a vertical caulked joint separation. The panels are structurally bonded to interior vertical window framing members only and thus no vertical framing members are visible on the exterior side, only the caulked joint. The panels are installed, glazed and caulked by workers operating on scaffolding along the building exterior.
A typical installation technique is as follows. A continuous frame head member which is a channel-shaped aluminum extrusion having an inverted U-shaped section is secured to the upper portion of the building window structure. A continuous frame sill member which is a channel-shaped aluminum extrusion having a U-shaped section is secured to the lower portion of the window structure. The frame head and sill are a permanent part of the window structure. Vertical impost framing members which are usually rectangular hollow aluminum extrusions are secured to the frame head and sill members, running vertically and spaced to accommodate required panel widths. The glass panel is then installed on-site from the building exterior, being tilted in at the top and then dropped down so that the bottom end portion of the glass panel locates in the frame sill channel, the upper end portion of the glass panel locates in the frame head channel and the vertical joint between the panels occurs in front of and overlaps the secured vertical imposts. Neoprene strips having a wedge-shaped section are forced between the rear of the glass panel and the frame head and sill members so as to urge the glass panel against the horizontal gasket strips secured to the frame head and sill thereby sealing the glass panel horizontal perimeters. Multiple glass panels are arranged side-by-side and secured and sealed between the frame head and sill in this manner, overlapping the imposts.
The exterior vertical butt joints between adjacent glass panels and the interior structural joints between the glass and imposts must then be sealed. The latter is done on-site by inserting a silicone compatible spacer gasket between the interior glass surface and impost finished off on top with a bead of gun-grade structural silicone on each glass edge. The glass panels must then be clamped from the exterior to the imposts while the structural silicone beads cure. This may take as long as two weeks. The clamps are then removed and, from the exterior, a back-up rod is inserted at the exterior butt joints between panels followed by an overlay bead of silicone culking to seal the joint.
In the system described, the outer legs or apron portions of the frame head and frame sill which overlap and secure the glass are visible from the building exterior. The exterior vertical joints between panels however are merely caulked; thus no aluminum members are visible. This is known as a two sided vertical butt glaze system. Conventional "wet" installation of a two sided butt glaze system requires glazing on-site, usually totally from the building exterior, with a substantial lapse in time between glazing and final caulking of the exterior butt joints. In addition, the replacement of a broken panel requires the remnants of the panel to be separate from the mullions with subsequent re-glazing and re-caulking operations as previously described. Replacement, like installation, is therefore labor intensive and extremely costly.
The present invention is directed to rapidly installing a fully factory glazed two sided vertical butt glaze system from the building interior such that the vertical exterior glass panel butt joints are sealed during such installation and such that the glass panels can be replaced with minimal labor and expensive should it ever become necessary.